Electron discharge device



O. H. SCHADE o ooouooo Filed March 25, 1938 INVENTOR. OTTO H. SCHADE BY v ww ATTORNEY coocooxn.

ELECTRON DI SCHARGE DEVICE 1. 1 oo 0 o c c o 0 o 094 0 o 0 o o 0 Q 0 yo 0 o 0 0 o Get 4, 1938.

50 easily constructed. to or greater than the pitch d3 between the turns 50 I Patented Oct. 4, 193 8 Illt 2 1 g V I umrmsmrsj by mesne assignments, to Radio Corporation of America; aco rporationvof Delaware 'Application March 25, 1938,"SerialNo. 197,977

v Claims. (crest-27.5), g a, My invention relates to electron discharge trode comprising either a arrow pitch grid devices, more particularly to improvements in element adjacentthe cathode-and a second wider multi-grid tubes utilizing so-called screen grids. p tch grid element spaced from the first grid In multi-g'rid tubes employing screen" grids element and electrically connected to the second 5 the control and screen grid electrodes have been grid which is in alignment with the screen grid. 5

positioned with their turns or apertures in align-1 The fine mesh or narrow pitc grid element can merit so that the control grid acts as'a shield" be pl ed y a v r mu r lement- Th for the screen grid to reduce the screen current. wider pitch grid element o the Signal grid c s However, difficulties are introduced when the the electrons so that they p ough the grid V control grid has either a fine mesh Which con- Wire's; ofthe screen grid. It is, therefore, un- 10- struotio is used f r du ing a, tub having a necessary to align the narrow pitch or variable high amplification factor, orwhen the control mu control grid element and screen grids and grid has a variable pitch to provide a variable because of the wide 'spacing'between the turns mu grid. I both a e it becomesdimoultto of the coarse mesh or wide pitched element of 15 line up the screen grid with the control grid. In the control grid, the screen grid can be placed 16 the case of the fine mesh grid itis necessary to further y from thecohtrol d 80 s to rebring th screen grid close t th t ol id duce interelectrode capacity. At the same time so that the beams formed by the control grid t on l p n y beused between the turns will pass between the twins or through the Screen g dend the anode. 20 apertures of the screen grid and not strike the The novel features which I believe to be charsolid ortion or tu n of the screen grid, Th acteristic of my inventionare set forth with pareffect of this close spacing is to increase the tieulality in t appended C but t e inveninterele t d c pacit d intr d fu th tion itself 'will best be understood by reference undesirable effe t. Whe the screengriol i of to the followingdescriptiontaken in connection 25. very fine mesh and 'with the anode spaced; a? W e companying drawing in whichFigure conventional di tance from the soreeni id; tho 1 is a schematic section of an electron discharge screen current again increases due to the secon device e according to my invention n dary electrons emitted from the anode and either associated circuit, a d Figure 2 ws a m difi-r a suppressor grid is necessary or thean ode must cation of the tube Shown n u e 1 and its 3.0. be moved sufiiciently far away from the screen" associated circuit. l a grid to provide a space charge to suppress the I Referring to the drawing a e ec discharge s nda l t device made according to my invention comprises It isa principal object of my invention to an envelope ll] containing an indirectly heated provide an electron discharge device of the multiode II and anode l2. Positioned between grid type and utilizing a screen grid and having the cathode and anode re a pl r lity of grids, 35 a low screen current and high amplification one of which may be the Sc en grid In characteri tic, accordance with my invention I position between More specifically it is an object of my inventhe cathode and the screen grid a control election toprovide in multi-grid screen grid tubes a de l4 Comprising the narrow pitch grid e e- 40 novel type of control grid which results in a tube e it l5 d the Coarse mesh Wide pitch grid 40 having'a comparatively high amplification factor ment 6,'the two gr d elements being b t t th some ti a l screen r t, trically connected as at I! with the turns of the A ti further object of m i ti i t element l6 aligned with the turns of the screen provide a multi-grid screen grid tube in which a d l3- The input circuit I8 is connected befine pitch control grid or variable mu control tween the Control gridahd 0 0 ,and the out- 45 grid can be used adjacent the cathode but which put circuit l9 between the source of voltage nevertheless has a low screen current, low interpp y 20 d t e a ode l2. electrode capacity, and a high amplification For best results the distance d1 between grid factor, and a tube of this nature which may be element [5 and grid element l6 should be equal Briefly, a tube made according to my invenof the grid element I6 and the screen element l3.

tion comprises a cathode and an anode, and a The distance d2 between the element It and screen plurality of intermediate grids, one of saidgrids grid l3 should not be greater than the pitch de i being a screen grid and the other acontrol grid between the turns of the grid element to provide adjacent the cathode, the control grid or elecproper focusing. Inasmuch as the grid element 55 l6 and screen grid l3 have a wide pitch these grids can be easily aligned and because of the wide pitch they may be spaced some distance apart, thus reducing the interelectrode capacity between these two grids and between the signal grid and the anode l2. Thus, with the arrangement shown a high mu can be obtained but at the same time the screen grid current is substantially reduced. While shown as wire grids, the grids could be perforated sheet cylinder electrodes employing the principles set forth above.

In Figure 2 the narrow pitch grid element of the control electrode has been replaced by variable mu grid element l 5'. This tube has the same advantages however as the tube shown in Figure 1.

While I have indicated the preferred embodiments of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed Without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is:

1. An electron discharge device having an envelope containing a thermionic cathode and an anode-and a plurality of electrodes positioned between the cathode and the anode and including a screen grid electrode and a control electrode positioned between the screen grid electrode and the cathode and comprising a pair of spaced grid elements, the grid elements being electrically connected and wound with different pitches, the screen grid electrode and grid element of the control grid adjacent the screen grid electrode having the same pitch and being aligned.

2. An electron dischargedevice including an envelope containing a cathode and anode, and a plurality of electrodes between the cathode and anode and including a screen grid having a comparatively wide pitch, and a control electrode positioned between the cathode and screen grid and comprising a pair of spaced'grid-like elements electrically connected, the grid-like element adjacent said cathode having a comparatively narrow pitch with respect to said screen grid, and the grid element adjacent said screen grid having the same pitch as said screen grid, said screen grid and grid element adjacent said screen grid being aligned.

3. An electron discharge device having an envelope containing a thermionic cathode and an anode surrounding said cathode, and a plurality of concentric electrodes between said cathode and anode and including a helically wound screen grid having a comparatively wide pitch and a control electrode positioned between the cathode and screen grid and comprising a pair of spaced concentric helically wound grid elements, the grid element adjacent the cathode having a narrow pitch between turns and the grid element adjacent the screen grid having a pitch between turns equal to the pitch between the turns of the screen grid, the grid element adjacent the screen grid and said screen grid being aligned.

4. An electron discharge device including an envelope containing a cathode and an anode, and a plurality of electrodes between said cathode and anode and including a screen grid of com paratively wide pitch, and a control electrode between said cathode and screen grid and including a pair of spaced grid elements, the grid element adjacent said cathode having a comparatively narrow pitch and the grid element adjacent said screen grid having the same pitch as said screen grid with its turns in alignment with the turns of said screen grid, the spacing between said screen grid and said control electrode being not greater than the pitch of the grid element adjacent the screen grid.

5. An electron discharge device including an envelope containing a cathode and an anode, and a plurality of electrodes between said cathode and anode and including a screen grid of comparatively wide pitch, and a control electrode between said cathode and screen grid and including a pair of spaced grid elements, the grid adjacent said cathode having a comparatively narrow pitch and the grid adjacent said screen grid having the same pitch as said screen grid with its turns in alignment with the tlnns of said screen grid, the spacing between said screengrid and said control electrode being not greater than the pitch of the grid element adjacent said screen grid, and the distance between thegrid element adjacent the cathode and the grid element adjacent said screen grid being greater than the pitch of said screen grid.

OTTO H. SCHADE. 

